ACTS(wifi): Use shell command for setting country code

WifiManager.setCountryCode() is being removed, use the shell command to
set country code instead from ACTS tests.

Bug: 141107015
Test: Verified the changes
Change-Id: I23ebe57fcb8bed71b6b85ec1697e80bf150044f2
diff --git a/acts/tests/google/wifi/WifiMacRandomizationTest.py b/acts/tests/google/wifi/WifiMacRandomizationTest.py
index 5ad2188..4485220 100644
--- a/acts/tests/google/wifi/WifiMacRandomizationTest.py
+++ b/acts/tests/google/wifi/WifiMacRandomizationTest.py
@@ -435,8 +435,8 @@
             7. Verify the factory MAC is not leaked.
 
         """
-        self.dut.droid.wifiSetCountryCode(wutils.WifiEnums.CountryCode.US)
-        self.dut_client.droid.wifiSetCountryCode(wutils.WifiEnums.CountryCode.US)
+        wutils.set_wifi_country_code(self.dut, wutils.WifiEnums.CountryCode.US)
+        wutils.set_wifi_country_code(self.dut_client, wutils.WifiEnums.CountryCode.US)
         mac_sta = self.connect_to_network_and_verify_mac_randomization(
                 self.wpapsk_2g)
         softap = wutils.start_softap_and_verify(self, WIFI_CONFIG_APBAND_2G)